1. Field of the Invention
The present invention relates to a method and an apparatus for supporting the measurement of an object to be measured using a measurement part program. The present invention relates in particular to a measurement support method and apparatus wherein based on simplified shape definition data of a workpiece, an inspection of a measurement part program can be easily performed.
2. Description of the Related Art
In related art, a machine is controlled by using a numerical value controller and a part program to process or measure a workpiece. By automating the processing and the measurement, unattended processing and unattended measurement are provided. For such an unattended processing and measurement, however, a controller automatically controls a processing device and a measurement device in accordance with a part program. If the part program is imperfect, not only will normal processing and measurement not be performed, but also, depending on the imperfection, a machine may operate without following the program, or a collision between machines or between a machine and a workpiece may occur, thereby resulting in workpiece or machine damage. Therefore, before the processing and the measurement are actually performed, an inspection of the part program is inevitably required.
As the most generally employed inspection method, each instruction in a part program is confirmed by actually executing it for a machine. However, when this method is used to perform an inspection, considerable time must be expended and the costs involved are high. Further, since a machine must be employed for the inspection, the machine can not be used to perform processing and measurement and its actual working ratio is reduced.
According to another inspection method for a part program, a virtual inspection is performed by using a CAD system which created the part program. In this case, while the actual working ratio of a machine is not reduced, an expensive CAD system is required. Further, to operate the CAD system and obtain acceptable results, considerable skill is required, and mastering the operation of the CAD system is not an easy task for a user unfamiliar with computer manipulation operations.
Furthermore, as an example, a part program that has been inspected and satisfactorily executed may be partially altered and employed for a similar workpiece. In this case, since correction errors may occur, the inspection of the entire part program is also inevitable, regardless of how many program corrections have been made. Even when a part program is altered only partially, programming knowledge will inevitably be required; however, mastering a programming method is not easy.
Specifically, a related-art example for easily creating and changing a processing program is disclosed in JP-A-8-339215, wherein the trajectory of a tool and the shape to be processed are displayed based on processing program data, and a processing simulation is performed to create and change a part program. According to this example, shape drawing screen data are generated using the part program employed for the processing.
Another example is disclosed in JP-A-9-91019, wherein a commonly used file is prepared based on a contour data file, and a drawing and a processing program are generated.
Since in the commonly used processing a predetermined shape is obtained by cutting a workpiece, the final workpiece shape can be obtained by analyzing the trajectory of a tool (see JP-A-8-339215). Whereas, if the final workpiece shape can be defined, the acquisition of the processing trajectory or the creation of the drawing is possible (see JP-A-9-91019).
On the other hand, to prepare a measurement program, design data are converted to generate shape data that correspond to the shape of an object to be measured, and the shape data are employed to prepare a measurement procedure program while taking the measurement conditions into account (see JP-A-63-206607).
Further, the direction in which a probe advances and the advanced position and the approach position of the probe are calculated based on CAD data, and travel trajectory data are obtained to prepare an automatic contour measurement part program and a test program (see JP-A-3-288909).
In addition, a probe route program is created based on a CAD drawing, and the measurement results are written to the CAD drawing (see JP-A-8-29152).
Moreover, to generate a travel path based on CAD data and measurement data, an offset shape where a shape of an object to be measured is offset externally is created, and a travel path is generated along the offset shape (see JP-A-2000-161942) However, in this case, since the travel path is generated on a plane at a predetermined distance from a projection point of an object to be measured in order to prevent a probe and the object to be measured from interfering with each other, a longer than necessary travel distance is required, and an enormous amount of time is wasted during the measurement period.
As is described above, various devises are proposed for the creation of the measurement program.
For fear that there maybe an outflow of technical know-how, manufacturing security control has been tightened. For a workpiece for which performance can be estimated by analyzing the CAD data for the workpiece, the CAD data are kept secret and are not provided.
However, the above-mentioned related-art method generates a measurement part program based on CAD data. For example, only a measurement part program and data for a simple workpiece shape are provided. Therefore, when a CAD system or CAD data are not available, a problem still exists in that an inspection of a measurement part program is not easy as described above.
As previously described, for a processing part program, since a final workpiece shape can be obtained by analyzing the processing trajectory, an inspection of a part program is comparatively easily performed. However, a travel trajectory obtained using a measurement part program does not always match the shape of a workpiece. Further, it is very difficult to inspect which point of a workpiece is measured by a measurement part program, or to inspect whether or not a travel trajectory interferes with the workpiece.
Furthermore, a measurement part program created by a common CAD system generates a travel path on the plane at a predetermined distance from the projection point of an object to be measured in order to prevent interference between a probe and the object to be measured. Therefore, a longer distance than necessary is required, and an enormous amount of time is wasted during the measurement period. To resolve this problem, the travel path of the probe is reduced and optimized to improve the measurement efficiency. However, in this case, it is difficult to inspect a measurement part program that has been corrected.